One of our local archers, Dokusai no Gyoja, uses this type of bow so I
the Yumi question to him.
"The pistol grip effect is achieved by the te-no-uchi or grip with the left
hand. In essence, you just pull the bow into the cleft between the thumb
forefinger. With a slight articulation of the wrist (flexed toward the
arm) you get away with no forearm protection and also you are able to sort
of go inside the bow. Due to the asymetrical nature of the Yumi, you need
hold it so that the longer limb (upper) slants away from the body. So the
only way to shoot is with a pistol grip, but there is no kind of
anthropomorphic help in the design of the grip, which is virtualy
indistinguishable from the rest of the bow except that it is wrapped. You
have to achieve the pistol grip with your hand, and it's easy but much
harder than it sounds! Hope this helps. By the way, I should mention that
is not unusual for a Yumi to have a draw length of 40" or so, so kyudo may
have to be modified in some realms due to arrow restrictions."
Believe in Magic but Trust in Steel